Currently, one of our most exciting areas of research is our exploration of the intersection of biology and tensegrity robots. The inspiration for this research comes from the idea of “Biotensegrity” pioneered by Dr. Steven Levin, which holds that tensegrity structures are a good model for how forces move through our bodies. Thus, instead of the common sense “bone-centric” model where force passes comprehensively from bone to bone, one should take a fascia-centric view that looks at the global fascia network (i.e. continuous chains of muscles and ligaments) as the primary load paths in the body. (For more info on fascia see my prior posts fascia, bones, and muscles, and Fascia and Motion.).

Tom Flemons' Tensegrity Model of the Spine

To date, the vast majority of tensegrity research has focused on static tensegrity structures, but it turns out that they have many qualities which make them well suited for motion, especially the type of motion required of a robot (or animal) moving in the real world outside the safety of factories or laboratories. As I discuss in an earlier post, these advantages largely center around how tensegrity structures can distribute forces into the structure, instead of accumulating and magnifying forces through leverage, which is what happens in a normal rigidly connected robot.

Using the Tensegrity Robotics Simulator that we have been developing over the last year, we have been exploring biologically inspired tensegrity robots. Our initial focus is on a “snake” or “spine” like tensegrity robot, which is inspired by the models of a tensegrity spine created by Tom Flemons. For ease of modeling, our “snake” uses tetrahedron shaped elements, which look different from vertebrae, but maintain a similar topology of connectivity. Thus, each “vertebrae” of our snake is connected and controlled by cables to the next “vertebrae” and has no rigid hinges or joints. Compared to a regular robotic snake, this approach has the advantage that forces are not magnified via leverage through the body. As a result, we are able to explore real distributed control approaches because local actions stay predominately local without the unexpected global consequences experienced in a rigid robot.

In the following video we show our simulated “tensegrity snake” moving over different terrains while using a distributed and decentralized oscillatory control system. This first experiment uses controls with no world knowledge or motion planning, yet we see that it is capable of traversing a variety of complex terrains. Brian Tietz, a NASA Space Technology Research Fellow from Case Western Reserve University’s BioRobotics lab has been developing the snake tensegrity simulation and controls.

We have focused on distributed force controls because we want to maximize the competence of the structure’s interaction with the environment in order to simplify higher-level goal-oriented task controls. This approach mirrors the division between the mammalian spine, which is decentralized and primarily concerned with forces and rhythm, and the mammalian brain, which is concerned with task based motion planning and interfacing with the highly competent spine/body for execution.

Our work on distributed controls is influenced by theories of neuroscience that focus on networks of Central Pattern Generators (CPG) for distributed control of complex coordinated behaviors. We implemented a distributed (one controller per string) version of impedance control (which balances the needs of force and length control) on our simulated “tensegrity snake” robot and experimented with a variety of oscillatory controls on string tension and length. The version shown in the video implements a two level controller for each string, where the higher level control produces an open-loop sine wave for the tension control, and the lower level performs stabilizing feedback on position and velocity.

We found that even with this simple reactive control, our robot could generate a variety of gaits and navigate a wide range of obstacles which would normally require motion planning and structure specific gaits. We believe that this high level of motion competence at the reactive structural level will lead to impressive capabilities as we continue to explore closed loop CPG controls. We have initially focused on mobility tasks because recent research shows that neural-controls of goal-oriented manipulation are based in the same oscillatory controls found in mobility. Thus, as we mature our understanding of this new technology we will be able to extend it to goal-oriented manipulation tasks as we incorporate task-space sensory information.

A prototype tensegrity "snake" robot which will be used to verify the algorithms developed in simulation

Finally, to see more about our other research into dynamic tensegrity robots, please see my recent post on our SuperBall Bot project, where we are developing a planetary landing and mobility system with a tensegrity robot. Also, I have a video of a lecture on tensegrity robots and our physiology and neuroscience.

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About BeingHuman

Greetings!
Here you will find my thoughts on being human, based on my ongoing research into robotic and human motion, neuroscience, physiology, and machine learning. You will also find videos of my talks and papers from the Dynamic Tensegrity Robotics Lab which I lead at the NASA Ames Research Center.

Archive of all past posts

Archive of all past posts

My Favorite Ergonomic Equipment

Based on my understanding of human physiology and motion, here are some quick reviews on my favorite ergonomic tools. These are the ones I use at home and at work. I will add more in-depth posts discussing the alignment theory as I get them written.

FitBall Sitting Disc
Sitting Discs are a great way to train for Active Sitting. By destabilizing the surface you are sitting on, they engage your core muscles and keep you in dynamic motion while your body actively balances on the disk. I recommend the larger 15" disc. In Depth Review

Salli Saddle Stool
The Salli saddle stools are one of the best stools for Active Sitting. They hold your pelvis upright, so that your spine can be well aligned with gravity, while also allowing your knees to be lower than your hips to keep your hamstrings and hip-flexors from shortening. Actively sitting takes effort, so increase your time in the saddle slowly.

3M Ergonomic Mouse
The vertical design keeps the arm in a well aligned neutral "handshake" position that prevents the shoulder from rolling forward. By keeping your shoulders back and the scapula flat on your back you avoid many of the common sources of wrist pain. This is the biggest bang for your buck if you are having wrist pain. It comes in small and large sizes (small is linked below). Sadly, I have only seen it for right hands.

ErgoMagic Keyboard
Like the 3M mouse above, this keyboard allows you to have your hands in a more neutral vertical position which reduces many of the problems associated with wrist and shoulder pain. It also allows you to spread the key pads to be at shoulder width so that you don't have to twist your wrist like on a straight keyboard.

Sit-Stand Desk
A sit stand desks allows you to dance while working! It also allows you change between a variety of different sitting options and standing so that you don't get stuck in one position. The best option that I have found is from GeekDesk.com. I have two from them and they are the cheapest and have held up well. You can save even more money by buying just the base frame from GeekDesk and getting the table top from Ikea. You save on price and shipping is significantly less this way.

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Books I Recommend

Sync: How Order Emerges From Chaos In the Universe, Nature, and Daily Life
This book blew my mind.
Really -- this was probably one of the most influential books I've read in a decade. This points straight at the heart of what we intuitively recognize as the difference between living breathing organic aspects of nature and the mechanistic nature of human engineered system. It all boils down to oscillators and their ability to synchronize. This basic mathematical property is the basis for all the order that we see in the world -- and our ability to move -- and our ability to relate to each other -- and really everything. This is an easy and engaging read, and you will come away with new eyes for the world.

Anatomy of Movement
This was the best book I have read for learning about the function of my own body and is endlessly useful for anyone who is alive and moving in the world. Ever have pain when you make a specific motion and wonder what is going on? This book will help you isolate the muscles responsible for that motion. By showing how each muscle moves your body under different conditions, you will learn their *use* rather than just memorizing a bunch of names.

Anatomy Trains: Myofascial Meridians for Manual and Movement Therapists
This book is great to see and understand the complex network of tension in the living body, and to learn about fascia and how it works.

Rhythms of the Brain
This recently published book covers cutting edge theories of how the brain works. The key focus is on how the brain relies heavily on coupled oscillatory networks, timing loops, and synchronization. It also discusses how the activity in the brain can be viewed as a dynamic tensegrity structure. A more technical book, but well worth the effort!